Curiosity is expected to launch from Cape Canaveral Air Force Station in Florida on November 25, 2011, and will land on Mars in August 2012. The decision regarding its landing site is expected to be made this month

After recently retiring Mars rover Spirit, NASA is introducing a new Mars probe called Curiosity. While the rover is expected to launch later this year, one critical question remains unanswered: where will it land?

NASA rover Curiosity is a $2.5 billion, nuclear-powered machine that is the size of a Mini Cooper, and is four times as heavy as Spirit and Opportunity. Curiosity contains
a laser that can vaporize rocks at seven meters, a percussive drill, a
large robot arm and a weather station. In addition, it has 4.8kg of
plutonium-238.

Curiosity's main mission on Mars is to find organic compounds as a
"telltale sign" that life have existed on Mars. The problem is that
scientist's must decide on a landing area that will most likely contain
such evidence.

So far, scientist's have narrowed the choices down to four options:
Eberswalde Crater, Mawrth Vallis, Gale Crater and Holden Crater.

"Each site has things that make it good and things that make it not
quite so good," said planetary scientist Matt Golombek of NASA's Jet
Propulsion Laboratory in Pasadena, California. "It's kind of hard to
select because it boils down to which kind of science is important to
you, and that's almost personal."

Eberswalde Crater contains a delta, which is believed to be a buildup of sediment left by flowing water. This could be advantageous in finding preserved organics and biosignatures. However, these deposits could be just clay-dusted rocks, and if that's the case, the entire mission would be a waste of time. But Golombek notes that this particular crater has the highest chance of finding organics.

Mawrth Vallis has exposed valley walls that are almost as old as the planet at 3.7 billion years old. These walls contain a lot of Martian history, and are stacked hundreds of meters thick with exposed clays called phyllosilicates, which form in the presence of water, as well as sedimentary rocks. But the problem with this landing area is that scientist's do not know how it formed, and that the water may have been to acidic to support life.

Gale Crater features a mound of debris that is 3 miles above the crater floor, and contains layered deposits of sulfates and clays. This site is particularly interesting because its the only one that has both materials (sulfates and clays). But again, scientist's don't know how it formed.

Holden Crater is a 93-mile wide crater with gullies, which "tail off" into deposits that were covered in water at one time. In addition, the crater has many ancient rocks called breccia, which have fallen, broken and cemented together by landslides, meteor impact or floods.

While the landing site is still undecided, what scientist's do know is that the rover will land within a 12.4-by-15.5 mile targeted area, which is a very precise touchdown that could not be accomplished before, hence, certain sites couldn't be accomplished before. Curiosity will be able to achieve what other rovers couldn't between its precise landing technique and the use of 10 science instruments that will allow it to detect any organics present.

Curiosity is expected to launch from Cape Canaveral Air Force Station in Florida on November 25, 2011, and will land on Mars in August 2012. The decision regarding its landing site is expected to be made this month.